To quickly determine the frequency response of your room and loudspeakers, place the test microphone at the main listening position, run pink noise through the system and observe the the Octave module display. Set averaging to slow and use 1/3 or 1/6 Octave mode. You can then adjust the corresponding bands of your equalizer accordingly.
In the video demo a calibrated measurement microphone is connected to iPad dock connector using USB camera adapter. The app supports real-time microphone frequency response compensation:
For a quick reference get an inexpensive external mic such as Dayton Audio iMM-6 which is compatible with the iPhone and plugs directly into the headset jack.
Pro users may consider using a dedicated measurement mic such as miniDSP UMIK-1 Measurement Microphone. Each unit comes with individual calibration file, a tripod and USB cable. Requires Lightning to USB Camera Adapter.